More than a week after the Germanwings A320 crash, identification of the victims is still underway, and the fifty people involved in the search, are still trying to find the second of the aircraft’s black boxes. After the voice recorder, retrieving the FDR (flight data recorder), which records all flight data (aircraft speed, altitude, engine speed, flight controls position...) is paramount for the investigators to be able to piece together an accurate scenario of the disaster.

In concrete terms, the black box, which is in fact orange in order to facilitate its location, is highly resistant to heat, water and severe shock. Weighing 7 kg. (15 lbs.), it consists of a chassis and a reinforced housing called the ‘‘memory module’’, inside which is a memory card that stores data of the last 25 flight hours.

On the side of the flight data recorder, to help in the location of the black box, there is also a beacon, which activates as soon as it hits water. As soon this happens, an ultrasonic signal is emitted every second, for 30 days - although from 1st January 2018, this will increase to 90 days - however, in the case of a crash on land, no signal is emitted.

This is one difficulty at present facing the Germanwings accident investigators. In addition, the fact that the enormous amount of debris, scattered over the search area of around two hectares (five acres), on steep mountainous terrain, means that nine days after the accident, the second black box has still not been located.

Until the Germanwings crash, the retrieval of black boxes from terrestrial accidents posed no problem in particular. The question of installing a terrestrial beacon was never raised – but today it should be.